Differential duplex telegraph repeater



Jan. 10, 1928. 1,655,421

J. HERMAN DIFFERENTIAL DUPLEX TELEGRAPH REPEATER Filed June 26. 1926 INVENTOR Jflr/nm BY W I ATTORNEY Patented Jan. 10, 1928;

UNITED STATES PATENT OFFICE. 1

JOSEPH HERMAN, OF NEW YORK, N; Y., ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, AVC'ORPORATION OF NEW YORK.

DIFFERENTIAL DUPLEX TELEGRAPH BEBE-EATER.

Application filed June 26,"

in'iproved arrangements for reducing inter? ference with telegraph systems from alternating current power transmissiim'systems.

It has been the practice heretofore to employ reasonant shunts connected across the .recciving'relay windings of telegraph systems of the class to which the invention re,- lates. These shunt circuits are tuned to the frequency of the interfering power currents, offering a low impedance to these currents and a high impedance to the signaling currents.

In accordance with the invention described hereinafter, I provide an anti-resonant circuit in a novel arrangement, whereby a very high impedance is offered to power cur rents tending to flow into the repeater from the line.

The accompanying drawing shows in diagrammatic form a telegraph repeater circuit improved according to the invention. The telegraph repeater circuit consists of the telegraph line; the balancing artificial line, the sending relay and the source of direct current associated. therewith, and the receiving relay having one winding in the line and one winding in the artificial line.

7 The circuit ccmnectionsof the above are old and well understood in the art.

lVIy anti -resonant circuit consists of a transformer having winding \V connected iu series with the line and aywinding IV winner-ted in series with the artificialline, and of the condenser (I connected in shunt between the line and the artificial line. This circuit is tuned to the frequency of the inter :fering power current and offers a very high impedance to such currents flowing from the line.

I connect the windings IV and of the transformer differentially with respect to signals sent to the line by the sending relay of the repeater. Accordingly these windings have no effect on the signals from the i to flow 1926. Serial is. 118,692.

sending relay. This arrangement permits of greater discrimination against the inter feringccurrent at the other end of the circuit.

7 It will be understood that whereas it has been necessary heretofore to employ separate anti-resonant circuits in the line and in the artificial line of each repeater circuit, which arrangement affects both the transmitted and the received telegraph signals. I use. the

single and simple anti-resonant circuit arraiwement disclosed above, and connect the windings of the transformer as shown. thereby not only providing a very high impedance to the interfering currents tending into the repeater, but also permitting of greater discrimination at the other end of the telegraph system ing power currents.

\Vhat is claimed is: 1. In a differential duplex telegraph r'e peater system, a sending relay. a receiving relay, a line and an artificial line, a transformer having a first winding in series with against the interfersaid line anda second winding in series with said artificial line, said windings being connected-diiferentially with respect to signals sent to the line by said sending relay and a condenser in shunt with the windings of said transformer to form a tuned circuit antiresonant at the frequencies of interfering I alternating currents. v

'2. In a differential, duplex telegraph repeater systenna sending relay. a receiving relay, in line and an artificial line. a transformer having a lirstwiuding iii-series with said line and a second winding in series with said artificial line and a condensi-lr in shunt with said wiudings said windings being connected dilferentially with respect to nals sent to the line by said sendingrclay, and the inductance of said windings and the capacity of said condenser being such that a 'highimpedance iswoiferedt'o interfering alternating currents flowing in the line.

In testimony whereof, I have signed my name tothis specification this 24th day or, June, 1926.

JOSEPH HERMAN. 

